# alg.py
from typing import List

def find_subsequences(nums: List[int]) -> List[List[int]]:
    """
    找出所有非递减子序列（长度至少为2）
    """
    res = []

    def backtrack(start: int, path: List[int]):
        if len(path) >= 2:
            res.append(path[:])
        used = set()
        for i in range(start, len(nums)):
            if nums[i] in used:
                continue
            if not path or nums[i] >= path[-1]:
                used.add(nums[i])
                path.append(nums[i])
                backtrack(i + 1, path)
                path.pop()

    backtrack(0, [])
    return res
